Re: Stale description for pg_basebackup

From: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
To: masao(dot)fujii(at)oss(dot)nttdata(dot)com
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Stale description for pg_basebackup
Date: 2021-04-22 02:19:40
Message-ID: 20210422.111940.1395964312647296660.horikyota.ntt@gmail.com
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At Thu, 22 Apr 2021 10:56:10 +0900, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote in
>
>
> On 2021/04/22 9:25, Kyotaro Horiguchi wrote:
> >> What about the following description?
> >>
> >> -------------------
> >> When you are using -X none, if write activity on the primary is low,
> >> pg_basebackup may need to wait a long time for all WAL files required
> >> for
> >> the backup to be archived. It may be useful to run pg_switch_wal
> >> on the primary in order to trigger an immediate WAL file switch and
> >> archiving.
> >> -------------------
> > Looks far better.
>
> Patch attached. I appended the following description to assist
> users to understand why pg_basebackup may need wait a long time
> when write activity is low on the primary.
>
> ------------------
> pg_basebackup cannot force the standby to switch to
> a new WAL file at the end of backup.
> ------------------

I'm not sure which is the convention here, but I saw that some
function names in the doc are followed by parentheses (ie
pg_switch_wal()).

(prepended?) It seems a bit redundant but also a bit clearer. How
about the following simplification?

- It may be useful to run pg_switch_wal on the primary in order to
- trigger an immediate WAL file switch and archiving.
+ It may be useful to run pg_switch_wal() on the primary in that case.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center

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